Study On Abnormal Vibration Optimization Of A Heavy-Duty Semi-Trailer Tractor

In recent years,the competition in the commercial vehicle market has become increasingly fierce.The user market is phasing out some low-end heavy-duty commercial vehicle products.At the same time,the demands for improving heavy-duty commodity vehicles' NVH performance are getting higher and higher.And major automakers are improving the NVH comfort of commercial vehicles at a strategic height.The problem of abnormal driving vibration studied in this paper belongs to the typical vibration problem of commercial vehicles and is urgently needed to be solved.In this paper,the problem of abnormal vibration of a heavy-duty semi-trailer is studied.The reason of the problem is found by the combination of simulation and test,and a reasonable improvement scheme is proposed and the vehicle is verified.The main contents of this study are as follows:Firstly,through the subjective evaluation,the abnormal vibration problem is clarified as the in-vehicle pitching jitter on the straight road at a specific speed.After clarifying the abnormal vibration conditions and phenomena,a total of four types of objective test measurements are carried out: vehicle vibration abnormal road test,vehicle modal measurement,vehicle MTS 6 channel road simulation test and vehicle tire assembly radial run-out test.The road test selects the position of the driver's seat rail as an objective evaluation point,and the result proves that the vehicle's jitter frequency is equal to the tire rotation frequency.The vehicle modal test results show that there is a vehicle pitch mode at the driving jitter frequency,so the abnormal vibration problem is determined as the resonance problem.The MTS 6-channel bench test reproduces the abnormal vibration of the vehicle and confirms that the vehicle jitter problem mainly comes from the mid-rear axle tire excitation.The results of the vehicle tire assembly radial run-out test show that most of tire assemblies have large radial run-out peak-to-peak values.Then,build the multi-body dynamics model of the vehicle,and the simulation model is verified by the bench test.The methods of eliminating abnormal vibration are studied from the two aspects of excitation source and transmission path respectively.By simulating the excitation amplitude to simulate the tire radial run-out value(excitation source),various factors(transmission path)affecting the longitudinal vibration of the vehicle are analyzed and optimized.The results show that the control of the rear axle tire radial run-out,the use of the main and secondary spring structure and the leaf spring rubber support significantly improve the vehicle pitch and longitudinal vibration.Finally,by controlling the vehicle tire radial run-out and optimizing the rear suspension structure,the improved scheme was verified on the test vehicle,the vehicle pitching jitter problem was eliminated and experience was provided for subsequent product development.